Cost analysis for the degradation of highly concentrated textile dye wastewater with chemical oxidation H2O2/UV and biological treatment

The efficiency and cost‐effectiveness of H₂O₂/UV for the complete decolorization and mineralization of wastewater containing high concentrations of the textile dye Reactive Black 5 was examined. Oxidation until decolorization removed 200–300 mg g^?1 of the dissolved organic carbon (DOC). The specific energy consumption was dependent on the initial dye concentration: the higher concentration required a lower specific energy input on a weight basis (160 W h g^?1 RB5 for 2.1 g L^?1 versus 354 W h g^?1 RB5 for 0.5 g L^?1). Biodegradable compounds were formed, so that DOC removal could be increased by 30% in a following biological stage. However, in order to attain 800 mg g^?1 overall mineralization, 500 mg g^?1 of the DOC had to be oxidized in the H₂O₂/UV stage. A cost analysis showed that although the capital costs are much less for a H₂O₂/UV stage compared to ozonation, the operating costs are almost double those of ozonation. Thus, while H₂O₂/UV can compete with ozonation when the treatment goal only requires decolorization, ozonation is more cost‐effective in this case when mineralization is desired. Copyright © 2006 Society of Chemical Industry     

Combination of biological and chemical processes for the treatment of textile wastewater containing reactive dyes

The treatment of a segregated textile wastewater containing reactive dyes was investigated in two continuous‐flow process trains using ozonation and biological processes. The degree of decolorization and dissolved organic carbon (DOC) removal achieved by ozonation followed by aerobic treatment (two‐stage) was compared with that found when an anaerobic and aerobic pretreatment was added (four‐stage). Although the biological pretreatment reduced color by ～70%, similar amounts of ozone were required in both trains to achieve high degrees of overall removal of color and DOC. In both trains, ozonation increased biodegradability in the following aerobic reactor, however, in order to reach ～80% overall DOC removal, a specific ozone absorption (A*) of ～6 gO₃ gDOC_o^?1 was required and >50% of the DOC was mineralized in the ozone reactor. A comparison of cost estimates based on investment and operating costs for the process alternatives showed that a four‐stage train would reduce costs only if it enabled a decrease in A* to less than 2 gO₃ gDOC_o^?1. Difficulties in comparing treatment processes for segregated vs full‐stream wastewaters are discussed. Copyright © 2003 Society of Chemical Industry     

Application of Response Surface Methodology for Coffee Effluent Treatment by Ozone and Combined Ozone/UV

This paper reports a study using ozone (O₃) and combined ozone/ultraviolet (O₃/UV) processes for color removal and caffeine degradation from synthetic coffee wastewater using a second-order response surface methodology (RSM) with a three-level central composite face-centered (CCF) design. The effects of O₃ concentration, initial pH, and reaction time were examined for both processes. The reaction time and pH were statistically significant for caffeine degradation and color removal. In the ozonation process, higher caffeine degradation and color removal were observed in alkaline pH, indicating that ozone attacks indirectly, consequently generating hydroxyl radicals. Regarding the ozone/UV process, it was observed that lower caffeine degradation and color removal occurred at neutral pH, indicating an adverse effect due to lower ozone dissolution and consequently the production of a smaller amount of free hydroxyl radicals. The achieved results showed that the techniques were efficient for color removal (85% and 99%, respectively) and caffeine degradation (88% and 98%, respectively).     

Evaluation of O3/UV and O3/H2O2 as Practical Advanced Oxidation Processes for Degradation of 1,4-Dioxane

The degradation of 1,4-dioxane was investigated on a laboratory scale. The extents of degradation and/or removal of 1,4-dioxane by ozonation at pH 6–8, UV irradiation, aeration, and addition of H₂O₂ were very limited. On the other hand, the degradation of 1,4-dioxane by O₃/UV and O₃/H₂O₂ was accelerated compared with the above respective methods. The amounts of 1,4-dioxane degraded per amount of ozone consumed in O₃/UV and O₃/H₂O₂ were also higher than in ozonation. The amount of 1,4-dioxane degraded in O₃/UV was affected by the intensity of UV irradiation, and that in O₃/H₂O₂ was affected by the amount of H₂O₂ added only in the case of a high initial concentration of 1,4-dioxane.     

Ozone-Based Processes Applied to Municipal Secondary Effluents

This study analyzes the performances of 2 methods of oxidation based on ozone, namely ozonation and ozone combined with hydrogen peroxide (O₃/H₂O₂), on two biotreated municipal wastewater effluents. The main parameters monitored to evaluate the effectiveness of the processes were Chemical Oxygen Demand (COD), Dissolved Organic Carbon (DOC) and Biochemical Oxygen Demand (BOD₅). Ozonation and O₃/H₂O₂ treatment removed 44% and 48%, respectively, of the COD, after 90 min, of the secondary effluent of Calafell wastewater treatment plant (Spain). On the secondary effluent from the Grasse wastewater treatment plant (France), these same treatments (O₃; O₃/H₂O₂) achieved, respectively, a degradation of 52% and 100% of the COD after 60 min. The transferred ozone dose (TOD) during Calafell and Grasse effluents' ozonation were 122 mg·L^?1 and 77 mg·L^?1 after 90 min, respectively. A low removal of DOC was monitored during both O₃ or O₃/H₂O₂ treatments applied to Calafell wastewater, respectively 12% and 14%. Better DOC reductions were obtained on the water of Grasse treated with O₃ or O₃/H₂O₂, respectively, 48% and 60%. In addition, ammonia nitrogen was oxidized to nitrate nitrogen thus giving rise to an over ozone consumption. And finally, both processes proceeded with an increase of pH values. These results highlight the strong dependency of O₃ or O₃/H₂O₂ treatment effectiveness in terms of dissolved organic matter (DOM) removal and ozone consumption on wastewater composition (organic and inorganic substances).     

Ozone-Based Advanced Oxidation Processes for the Decomposition of N-Methyl-2-Pyrolidone in Aqueous Medium

The present study investigates the decomposition of N-Methyl-2-Pyrolidone (NMP) using conventional ozonation (O₃), ozonation in the presence of UV light (UV/O₃), hydrogen peroxide (O₃/H₂O₂), and UV/H₂O₂ processes under various experimental conditions. The influence of solution pH, ozone gas flow dosage, and H₂O₂ dosage on the degradation of NMP was studied. All ozone-based advanced oxidation processes (AOPs) were efficient in alkaline medium, whereas the UV/H₂O₂ process was efficient in acidic medium. Increasing ozone gas flow dosage would accelerate the degradation of NMP up to certain level beyond which no positive effect was observed in ozonation as well as UV light enhanced ozonation processes. Hydrogen peroxide dosage strongly influenced the degradation of NMP and a hydrogen peroxide dosage of 0.75 g/L and 0.5 g/L was found to be the optimum dosage in UV/H₂O₂ and O₃/H₂O₂ processes, respectively. The UV/O₃ process was most efficient in TOC removal. Overall it can be concluded that ozonation and ozone-based AOPs are promising processes for an efficient removal of NMP in wastewater.     

Post-Treatment of Pulp and Paper Industry Wastewater by Advanced Oxidation Processes

The aim of this study was to investigate the effectiveness of chemical oxidation by applying ozonation, combination of ozone and hydrogen peroxide and Fenton's processes for decolorization and residual chemical oxygen demand (COD) removal of biologically pretreated pulp and paper industry effluents. The batch tests were performed to determine the optimum operating conditions including pH, O₃, H₂O_2, and Fe²⁺ dosages. H₂O₂ addition reduced the reaction times for the same ozone dosages; however combinations of ozone/hydrogen peroxide were only faintly more effective than ozone alone for COD and color removals. In the Fenton‘s oxidation studies, the removal efficiencies of COD, color and ultraviolet absorbance at 254 nm (UV₂₅₄) for biologically treated pulp and paper industry effluents were found to be about 83, 95, and 89%, respectively. Experimental studies indicated that Fenton oxidation was a more effective process for the reduction of COD, color, and UV₂₅₄when compared to ozonation and ozone/hydrogen peroxide combination. Fenton oxidation was found to have less operating cost for color removal from wastewater per cubic meter than the cost for ozone and ozone/hydrogen peroxide applications.     

Application of Oxidation by a Combined Ozone/Ultraviolet Radiation System to the Treatment of Natural Water

When treating natural water, the simultaneous use of ozone and UV rays can lead to high level oxidation of the ozone–refractory organics. The main parameters affecting the efficiency of the O₃/UV system are: the ozonation rate, the average UV radiation intensity, the pH measurement, alkalinity, and the type of compound to be oxidized.

In optimum Ou/UV system application conditions, the abatement of COD in water from the Seine river is never above 30%. On the other hand, TOC removal is increased in weakly carbonated pond water loaded with humic matter. The O₃/UV system also ensures oxidation of saturated volatile organic halogens, with the exception of carbon tetrachloride.     

Post-Treatment of Composting Leachate by Ozonation

The post-treatment of composting leachate via an ozonation process in laboratory scale was studied in batch mode. According to the experiments, the COD removal was 47% after 30 min of ozonation via 0.4 g/h ozone (equivalent to 2.8 mg O₃/mg COD removed) at pH 9. In this circumstance, the removal of color and turbidity was also 86% and 89%, respectively. Increasing the ozone mass flow rate higher than 0.4 g/h had no considerable effect on the process variables. However, increasing the reaction time had a significant effect on both the removal of color and on COD of the leachate. Experimental data indicated that complete removal of color and 51% removal of COD were achieved after about 40 min of ozonation via 0.4 g/h ozone (equivalent to 3.3 mg O₃/mg COD removed). The ozone consumption rate increased as the reaction progressed and reached 4.1 mg O₃/mg COD removed after 60 min.     

Comparison of Different Oxidation Methods for Recalcitrance Removal of Landfill Leachate

In this work several oxidation methods, such as conventional ozonation, O₃/UV, O₃/UV/ferrous iron and Fenton oxidation, for the removal of recalcitrant organic matter present in landfill leachates are evaluated. The samples of the leachate are taken after a biological treatment and membrane ultra-filtration (UF). The contribution of the UV radiation and the effect of ferrous iron ions on the ozone process efficiency is discussed. At lower ozone dosages, the partial oxidation efficiency is reduced as compared to conventional ozonation and therefore, a higher degree of mineralization of the organic matter is achieved. Finally, the best results are obtained by the Fenton oxidation, however, based on economic considerations this method is not recommended.     

Decolorization of Wastewater Produced in a Pyrolysis Process by Ozone: Enhancing the Performance of Ozonation

This paper shows the results of color removal from a wastewater produced in a plastic pyrolysis process by ozonation. The influence of parameters such as temperature, reactor geometry, UVA, ozone input, and finally spraying of wastewater on performance enhancement of the decolorization process will be discussed. Due to the long residence time of O₃ molecules in the gaseous phase, recycling and spraying the wastewater in a pre-filled ozone chamber show a remarkable effect on decreasing the decolorization process time. At the end of this paper, an application of “micro-bubble producer” in this field, and its advantages will be introduced.     

Soil Fulvic Acid Degradation By Ozone In Aqueous Medium

Armadale Armadale soil fulvic acid (SFA) was found to contain several loosely bound organic impurities which could be removed by ethyl acetate extraction. The ozonation of purified Armadale SFA at a variety of dosages was characterized by monitoring the UV absorbance, weight loss, pH changes, total acidity, molecular weight and elemental composition. SFA could only be partially degraded even under ozone dosages as high as SFA/O₃ (w/w) of 1:6. At high ozone dosages (SFA/O3 1:6) mostly aliphatic compounds rich in oxygen were produced, whereas at low ozone dosages (SFA/O₃ < 1:0.5) mainly benzene polycarboxylic acids and polyhydroxy benzene polycarboxylic acids were found. The solid material bisolated from the chlorination (0.5 mg/L residual level) of residues from the ozonation (SFA/O₃ 1:0.2 to 1:0.5) of Contech SFA did not contain any chlorinated products.     

Comparison of Ozone and Hydroxyl Radical-Induced Oxidation of Chlorinated Hydrocarbons in Water

The efficiency of ozonation and advanced oxidation processes such as ozone/UV, ozone/H₂O₂ and H₂O₂/UV was assessed for chlorinated hydrocarbons using a closed batch-type system. 1,1-Dichloropropene (DCPE), trichloroethylene (TCE), 1-chloropentane (CPA), and 1,2-dichloroethane (DCA) were used as model compounds.

The direct reaction between substrates and ozone predominated at lower pH, which resulted in the efficient oxidation of the olefin, DCPE. At higher pH, ozonation resulted in more efficient oxidation of the chlorinated alkanes, with a corresponding decrease in the efficiency of DCPE oxidation. Consistent results were observed for ozone/H₂O₂ and ozone/UV treatment. Due to slow UV-induced decomposition of H₂O₂, the process using H₂O₂/UV (254 nm) resulted in very slow oxidation of all four compounds.

The total ozone requirement to achieve a given degree of elimination (to 37% of the original concentration), δ0.37, was used to assess the combined effects of the direct and indirect reactions for different types of waters.     

Effects Of Ozone On The Production Of Biodegradable Dissolved Organic Carbon (BDOC) During Water Treatment

This article deals with the oxidation effect of ozone on the increasing fraction of biodegradable organic matter with the “ozotest” method, a laboratory technique which simulates the effect of ozonation and allows a complete oxidation assessment. Ozone treatment was performed on river water samples and sand filter effluent samples. Ozone consumption, reduction of UV absorbance and BDOC formation were monitored with applied ozone doses from 0 to 10 mg/L and with contact times from 0 to 60 min. The BDOC formation was optimum at an applied ozone dose of 0.25-0.5 mg O₃ per mg DOC (contact time = 5 min) corresponding to apparition of traces of residual ozone and maximum UV reduction. Maximum ozone consumption, UV reduction and BDOC formation occurred simultaneously during the first two minutes of treatment. Concerning BDOC formation, applied ozone dose showed a greater effectiveness than contact time. For the same quantity of consumed ozone, a short contact time associated with a high ozone dose was preferable to a long contact time and a low ozone dose.     

Optimum Ozone Dosage of Preozonation and Characteristic Change of Refractory Organics in Landfill Leachate

Preozonation on landfill leachate was carried out. COD removal rate has an obvious inflection at ozone dosage 0.186 mg_O3/mg_COD in ozonation process. Seven sets of identical O₃-SBR combined process under different ozone dosages were studied. The results indicated that the best COD removal rate of synergetic effect is also at 0.186 mg_O3/mg_COD. New organic substances produced after ozonation was confirmed by an excitation-emission matrix (EEM). Carbon dioxide production increased from 36.3 mg to 75.7 mg after ozonation, confirming that biodegradability of refractory organics in landfill leachate was enhanced. All the arguments indicated that the inflection point of COD removal by ozonation has a great significance for preozonation.     

Oxidation of 1,3,5‐trichlorobenzene using advanced oxidation processes

The oxidation of 1,3,5‐trichlorobenzene (TCB) by ozone, ozone/UV, ozone/H₂O₂ and ozone/UV/H₂O₂ was studied. All studies were conducted in a continuously‐flowing completely mixed reactor (CFCMR), operated at steady‐state conditions using a hydraulic retention time of 10 minutes. The greatest removal of TCB using ozone/H₂O₂ treatment was achieved using a H₂O₂ concentration of 60 μM. At low pH values (approx. 2) ozone/UV performed significantly better than either ozone alone or ozone/H₂O₂. However, at circumneutral pH, the removal efficiencies of TCB by ozone/UV and ozone/H₂O₂ and ozone/UV/H₂O₂ were essentially equal (～ 97% for TCB). The removal efficiency of ozone alone was ～93% for TCB. At high pH (> 9) there was no advantage in supplementing ozone with either UV or H₂O₂ as the removal efficiencies for all processes studied were essentially equal.

The effect of humic acid and bicarbonate on the removal of TCB was studied. At 1.6 mg/L humic acid, 92–95% of the TCB was oxidized by the processes studied. The removal of TCB by ozone alone was significantly affected by the presence of bicarbonate ion. For the other processes at 10 mM bicarbonate, approximately 80% of the TCB was oxidized.     

The Combination of Ozone/Hydrogen Peroxide and Ozone/UV Radiation for Reduction of Trihalomethane Formation Potential in Surface Water

Applied ozone dosages of 20, 25, and 30 mg/L to lake water utilized by the city of Shreveport, LA produced no significant reductions in trihalomethane formation potentials (THMFP). However, the addition of 20 mg/L of hydrogen peroxide and/or 0.67 W/L of UV radiation (254 nm) in combination with ozone produced decreases in THMFP of over 60% in 60 minutes. Smaller THMFP decreases were seen with shorter contact times. The use of H₂O₂ and/or UV in combination with O₃ increased the percentage of applied ozone consumed by the lake water (i.e., enhanced the ozone mass transfer) five times over simple ozonation.     

Disinfection of Seawater: Application of UV and Ozone

Ozone and ultraviolet technologies are proposed as potential disinfecting agents for seawater. Ozone doses were applied in the range 0.38 to 4.89 mg O₃ L^?1. They permit to observe a complete disinfection as well as UV doses superior to 320 J L^?1. Impacts of both processes on organic matter were also studied. UV absorbances were reduced in both cases but in higher proportion using ozone (up to 50% removal). Total organic carbon was slightly reduced by UV radiation, and ozonation achieves up to 10% mineralization. Ozone reaction proceeds with biochemical oxygen demand increase. Seawater ozonation, in addition, leads to the formation of residual oxidants that show an inhibitory effect on autochthonous microorganisms.     

The Formation of Filter-Removable Biodegradable Organic Matter During Ozonation

Biodegradable organic matter formed during the ozonation of natural waters was fractionated into rapidly and slowly degradable components based on measurements of biodegradable organic carbon (BDOC). The rapidly degradable fraction (BDOC_rapid) was defined using the specific BDOC reactor incubation time that resulted in biodegradation similar to that in a pilot scale biofilter. Ozone dose was found to increase the formation of BDOC_rapid up to a transferred dose of 1.0 to 1.5 mg O₃/mg DOC. This fraction was insensitive to DOC quantity or character. The formation of BDOC_slow was not sensitive to ozone dose but was sensitive to DOC quantity.     

Ozone treatment of textile effluents and dyes: effect of applied ozone dose,pH and dye concentration

The ozonation of wastewater supplied from a treatment plant (Samples A and B) and dye‐bath effluent (Sample C) from a dyeing and finishing mill and acid dye solutions in a semi‐batch reactor has been examined to explore the impact of ozone dose, pH, and initial dye concentration. Results revealed that the apparent rate constants were raised with increases in applied ozone dose and pH, and decreases in initial dye concentration. While the color removal efficiencies of both wastewater Samples A and C for 15 min ozonation at high ozone dosage were 95 and 97%, respectively, these were 81 and 87%, respectively at low ozone dosage. The chemical oxygen demand (COD) and dissolved organic carbon (DOC) removal efficiencies at several ozone dose applications for a 15 min ozonation time were in the ranges of 15–46% and 10–20%, respectively for Sample A and 15–33% and 9–19% respectively for Sample C. Ozone consumption per unit color, COD and DOC removal at any time was found to be almost the same while the applied ozone dose was different. Ozonation could improve the BOD₅ (biological oxygen demand) COD ratio of Sample A by 1.6 times with 300 mg dm^?3 ozone consumption. Ozonation of acid dyes was a pseudo‐first order reaction with respect to dye. Increases in dye concentration increased specific ozone consumption. Specific ozone consumption for Acid Red 183 (AR‐183) dye solution with a concentration of 50 mg dm^?3 rose from 0.32 to 0.72 mg‐O₃ per mg dye decomposed as the dye concentration was increased to 500 mg dm^?3. © 2002 Society of Chemical Industry